Methods of measuring currency limpness

ABSTRACT

Measuring the limpness of a note is necessary to separate a worn note out of circulation. Several methods are disclosed which can be used either alone or in combination to test for limpness. One method measures the note&#39;s ability to reflect light or transmit the light. Another method measures the response of the note to an acoustic wave. Another method measures the note&#39;s deflection to a pressure or force. Yet another method measures the dielectric value of the note when placed between the plates of a capacitor. A final method involves measuring the thermal conductivity of the note. In each case, a limp note will produce distinguishable results from a stiff note.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a Divisional Continuing Application from prior application Ser.No. 08/730,711 filed on Oct. 15, 1996.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to methods of measuring the limpness ofcurrency. Specifically, the currency, in the form of paper notes, issubjected to a test or a series of tests to determine if it has wornbeyond an acceptable level of limpness.

BACKGROUND OF THE INVENTION

Automated, high-volume currency processing is a growing internationalindustry affecting numerous aspects of the distribution, collection, andaccounting of paper currency. Currency processing machines can bedesigned to detect numerous features of currency notes that pass severaldetectors on a conveyor in order to sort the currency and identifycounterfeit or reject notes. For example, prior art currency processingmachines are capable of detecting various physical characteristics ofnotes such as soiling level, optical quality, rips and tears, and canquantify missing portions of the notes. Data collected by detecting oneor more of these physical characteristics can be compared to a setfitness standard when determining if an individual note should berejected, and thereby taken out of circulation, or sorted for futuredistribution.

Currency notes are typically embedded with fibers, for example cottonfibers and wood pulp, giving the note a certain level of rigidity orstiffness. As the note is placed in circulation and manipulated while inuse, the fibers gradually break down and the note loses its rigidity,or, conversely, the limpness of the note increases with use. Limp notespose a number of problems in commerce. For example, limp notes can jamor tear in automatic currency handling devices. Likewise, torn currencyposes a problem for merchants who do not want to risk accepting currencythat is not negotiable. It may be more difficult to detect counterfeitnotes from authentic currency if the notes are badly worn and limp.Therefore, a need exists for a method of testing currency for limpness.By developing a method for determining the limpness of a single note, acurrency processing machine could be used to incorporate this methodwith other tests for physical characteristics of a note to moreaccurately determine if a note should be pulled from circulation. Thesingle parameter of a note limpness could also provide a standard forrejecting a note. With this new detection method of quantifying thelimpness of a note, currency distributors would also have a tool formonitoring the average lifespan of notes in circulation by comparinglimpness measurements with the date of initial circulation of notesprocessed.

The present invention provides various methods for determining thelimpness of a note and, thereby, addressing the many needs fordetermining this physical characteristic.

SUMMARY OF INVENTION

Several methods have been developed to measure the relative limpness ofa note. There is no absolute value for limpness above which an issuingauthority will pull a note from circulation. Instead, a value can bedetermined which is relative to a new note or some other standard. Themethods measure any combination of factors including the lightreflectivity of the note or the transmissivity of the note to light. Itsability to reflect or transmit acoustic waves can be measured. Further,its ability to resist deflection can be used as a measure of limpness.The dielectric value of the note can also be measured by placing thenote between the flat plates of a capacitor. Finally, the note's thermalhysteresis can be measured. In each of these methods, the performance ofa worn, limp note differs from the performance of a new, stiff note.

These methods can be used alone or in combination. Further, any singletest can be applied several times to different areas of the same note.By accumulating more than a single test result, the likelihood ofseparating an acceptable note or passing a limp note will be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects and advantages of the present invention will becomeapparent from the following detailed description when read inconjunction with the accompanying drawings, in which:

FIGS. 1a and 1b illustrate a new and stiff note of currency and a limpor worn note, respectively;

FIG. 2 illustrates the limpness test utilizing either the reflectivityor transmissivity of the worn note;

FIG. 3 illustrates the use of an acoustic source and detector to measurethe limpness of a note;

FIG. 4 illustrates the use of air pressure to deflect a portion of anote to determine the limpness of the note;

FIG. 5 illustrates the use of the dielectric value of the note stock todetermine the limpness of the note; and,

FIG. 6 illustrates a method of heating a note and measuring its heatcapacity to determine limpness.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

The present invention relates to methods of determining the limpness ofcurrency. The currency of many nations is commonly printed on specialpapers which are resilient and difficult to duplicate. The papercurrency, when initially printed, is very stiff. This stiffness is theresult of long fibers embedded in the paper. For example, manycurrencies use papers with cotton fiber content. These cotton fibersprovide much of the strength and stiffness to the note. However, duringuse, the note will be folded and crumpled and otherwise handled roughly.This rough handling will over time break down the embedded fiber,resulting in a note that is noticeably limper than new currency.

FIG. 1a illustrates a new, stiff note 10. The note contains fibers whichare mixed throughout the thickness of the note. The fibers are notnecessarily oriented in any particular direction. But, the sum of theirindividual stiffness results in the overall stiffness of the note. FIG.1b illustrates a similar note 10a which has been used in circulation.Over time the note will develop crinkles 11 along which embedded fibershave become weakened or broken. Eventually, the entire note may becomesoft and limp as numerous embedded fibers are worn down and broken. Thelimpness of the note makes it less suitable for use in commerce. It ismore likely to tear or jam in automatic currency handling devices. Limpnotes are also more susceptible to tearing in ordinary use and aregenerally less durable than stiff notes. Thus, it is desirable to removelimp notes from circulation.

FIG. 2 illustrates the use of a light source 12 to measure the limpnessof a note 10. The light source 12 emits a light beam 14. The beam can becoherent. A portion 16 of the light 14 will be reflected off of thesurface of the note, while a portion 18 will pass through the note. Adetector 20, or an array of detectors, can be placed near the note tomeasure the reflected light 16, while another detector 22 can be used tomeasure the transmitted light 18. Various light sources can be used. Ifreflected light is to be the measure, an ultraviolet light source ispreferred. If transmitted light is the measure, then an infrared sourceis preferred. Suitable detectors must be used to detect the reflected ortransmitted light. A photomultiplier or a silicon photo diode can alsobe used to amplify the signal produced by the reflected or transmittedlight. A limper note will tend to scatter more light than a crisp note,thus producing a lower relative signal from the reflected light detector20 or a broader reflective pattern across an array of detectors.Conversely, a limper note will allow more infrared light to pass,resulting in a higher relative output signal from the infrared detector22.

FIG. 3 illustrates a method of measuring limpness by testing theresponse of the note 10 to an acoustic source 24. The acoustic source 24will produce an acoustic output wave 26 which will impact the surface ofthe note 10. The wave will be partly absorbed, and also partlyreflected. The reflected portion 28 can be detected by a detector 30.The limper a note, the more energy it will absorb from the acoustic wave26. This results in a lower relative output from the acoustic detector30. A suitable acoustic wave source would be a piezoelectric transmitterreceiver pair.

A limper note 10 also will display a lowered resistance to deflection. Atest for limpness can therefore involve the application of a pressure tothe note and a measurement of its deflection. FIG. 4 illustrates such amethod. The note 10 can be sustained in a series of clamps 32 in such away that a portion 10b of the note is cantilevered. An air pressuresource 34 positioned near this cantilevered portion 10b of the note canapply a burst of air pressure 36. The pressure will tend to deflect thenote. A limp note will deflect further than a stiff note. Sensing theamount of deflection can be accomplished any number of ways. Forexample, optical sensors can be positioned so that the deflected noteswill block a beam directed at a sensor if the note is deflected morethan a predetermined distance. Another method of sensing the deflectionsinvolves using the cantilevered portion 10b of the note as thedielectric between the plates 38, 40 of a capacitor. The movement of thenote will change the overall value of the capacitor. Thus, a measurementof the capacitor's value will provide an indication of the movement, andhence limpness, of the note.

In a related method of detection of limpness, an undisturbed note 10 issimply used as the dielectric in a capacitor and placed between theplates 38, 40 of a capacitor, as shown in FIG. 5. The capacitor valuevaries according to the number of broken fibers in the detected area ofthe note. Therefore, a relative capacitor valve can be correlated to thelimpness of the note.

Another method involves a measurement of the heat capacity of the note.In other words, the note's ability to dissipate heat is a function ofthe notes limpness and wear. In this method, as shown in FIG. 6, aportion 10c of the note 10 is heated by a thermal source 42 to a firsttemperature. At a predetermined time, the temperature of that sameportion is measured by a thermal detector 44. The difference intemperature can be translated into a thermal conductivity or hysteresiscoefficient for the note. This coefficient is related to the limpness ofthe note.

A currency processing apparatus for measuring the limpness of noteswould necessarily transport the notes from a first location to a secondlocation while performing the tests and separating the limp notes fromthe stiff notes. For the thermal conductivity test discussed above, thenote might be heated at the beginning of the process and measured at asecond location to allow time for cooling. However, a test for lightreflectivity would be measured almost simultaneously with theapplication of the test light. The currency processing apparatus wouldhave a transport mechanism, which takes the note between various testlocations. The apparatus could utilize any single one of the abovementioned tests by itself or in combination with any of the other tests.For example, the deflection test could be coupled with the acousticresponse test. A combination of tests could produce a more completeseparation of limp notes. Further, any one of these test could beperformed on more than one test area on the note. This would take intoaccount variations across the surface of the note. For example, thelight reflectivity or transmissivity test could be performed on two orthree locations on any single note.

Although preferred embodiments of the present invention have beendescribed in the foregoing Detailed Description and illustrated in theaccompanying drawings, it will be understood that the invention is notlimited to the embodiments disclosed, but is capable of numerousrearrangements, modifications, and substitutions of parts and elementswithout departing from the spirit of the invention. Accordingly, thepresent invention is intended to encompass such rearrangements,modifications, and substitutions of parts and elements as fall withinthe scope of the appended claims.

I claim:
 1. A method of measuring a limpness of a note comprising thesteps of:(a) capturing the note between a capacitor's plates; (b)measuring the capacitor's value; and (c) determining the limpness ofsaid note from the measured capacitor's value.
 2. The method of claim 1,wherein the step of determining the limpness of said note furthercomprises correlating the capacitor's value to a limpness value.
 3. Themethod of claim 1 wherein step (c) comprises determining the limpness ofthe note from the measured capacitor's value at one or more locations onthe note.
 4. The method of claim 1 wherein step (c) comprisesdetermining the limpness of the note from the measured capacitor's valuealong with a second method for determining currency limpness todetermine a limpness value.
 5. The method of claim 4 wherein the secondmethod for determining currency limpness comprises the steps of:(a)emitting a light so it is incident on the note; (b) measuring an amountof the light reflected off of the note; and, (c) determining thelimpness of the note from the measured portion of the light.
 6. Themethod of claim 4 wherein the second method for determining currencylimpness comprises the steps of:(a) emitting a light so it is incidenton the note; (b) measuring an amount of the light transmitted throughthe note; and, (c) determining the limpness of the note from themeasured portion of the light.
 7. The method of claim 4 wherein thesecond method for determining currency limpness comprises the stepsof:(a) capturing a first portion of the note; (b) deflecting a secondportion of the note with a pressure; (c) measuring the deflection; and,(d) determining the limpness of the note from the measured deflection.8. An apparatus for determining the limpness of a note, said apparatuscomprising:(a) two opposed plates forming a capacitor; (b) a capacitancemeasuring device electrically connected to said capacitor; and (c) meansconnected to said capacitance measuring device for determining thelimpness of the note under test from the capacitance measured by saidcapacitance measuring device when said note is between said capacitorplates.